Slip clutch for propellers



Aug 5, 1952 E. c. KIEKHAEFER 2,605,850

SLIP CLUTCH FOR PROPELLERS Filed June 8, 1949 WM d@ sectioned.

Patented Aug. 5, 1952 .Kiekhaiefeig Ged-arbur.g".Viis. I

r .Applica-nomins'. 1949.sernmoz '97,135

x zexolaims.: (C1. 17u-@13575) vkv'This' invention relates' tol propellers-forout` board motors and the; like; and' particularly to means' for protectingtheA propeller from"darnage. ",The invention provides a slip `clutch"withinrthe hub 'ofthe' propeller through which therot-ational forcesuofthe shaft; carrying the'propeller'- are transmitted which comprises a seresfof Ydiscs an ,Iam spring carriedby `the shaft biasing-'the propeller axially in -thejdirection; offprppeller thrust to `effecttherewithgthe operativenessof :the discsk j, .t .v jojbiectlofthejnyentionlisjto providei aiclutch which isinstantly disengaged when' the propeller strikes a submerged b bjeict tojprevent damage ,to thepropeller. j j K Amore particular v.Objectis to reducejtheraxial travel of theji propeller on ith-e shaft' requiredxto operate ,the ,clutch whenthet propeller strikes a vsvllnierged object.v

' .Aliother object. is vto, :provide protectionKl of -the propellerthroughout thek range,A of Operation of 151391111312012 4 [A fore particular. object isto, ensure the` required frictional engagement ofthe 'clutchfdscs independently.ofsthethrust ofL the propeller., as required tto rprevent'slippage at peak loads.'

Another object of l:the invention is togjpr'event yburning,out of .the ,clutchunit Y v,`These?andfotlrier.objects and` advantages ofthe ritionawillF brel; "fullyf,v set lforthingthe folldwing,4 description, of. a. preferred. ,embodiment oggthe inyentionfj as illustrated'y inthe! accompany# .ieefdrawings. l Inthe drawings; y Eigvure lfisfa-sideeleyation of th'e'lwer end pro# peller unit of an outboard motor with a portion thereof and ofith@ propellery hub broken away and Fig. 2 is a view similar toFig. 1 'showing the propeller hub and slip clutch'disassembled'from the propeller-shaft; y

Fig.;3 is a transversesection tali-enen line sei-Sorfiarn f.; L i Flare isa transrese sectanitaken OnflineA-fof Fig. 1; and

Fig. 5 is an end unit.

In the drawing, the lower end unit I for an outboard motor, as shown, carries the propeller shaft 2 and the propeller 3 mounted on shaft 2 rear- Wardly of the unit. The streamlined, hollow hub 4 of the propeller carrying the blades 5 is of circular cross-section throughout and houses the friction disc clutch unit 6. as will be described.

The bushing 1 of unit 6 is mounted on shaft 2 elevation of the propeller atfthe forwardfendofqthe splined section-#Bof shaft2 and supports the forward end ofhubdifor freegrotation thereon. The transverse Ysection 9 'fnear the rie-arn of" hub- 4 -issupported-directly upon shaft"2 freelyV with-respect to-the splined section 8A and isprovided with flat,V circular-forwardand rear clutch faces i0 Vand. H vrespectively'.

y Thewinner splines 12in hubli--extend forwardly and rearwardly of section Syvv'ithirrhub1'41v The friction clutch discs I3 and vI tare dispose'd'fwithin hubldbetweenfbushing 1 `and section 9 ofthe-hub and are alternately arranged. 'Discs I3fa-reinternally splined to t on and engage the splined section 8 of shaft 2 and vare free to rotate-within hub; 4. `Discs I4 are free to rotate on' shaft 2 and are externally splined to engage; splinesv I2 of hub 4 to rot-ate therewith.

A.limited axial movement of hub 4 vis provided for on shaft 2 and bushing`1 so that-discs I3' and I4 maybe moved axially iinto. 'varying frictional engagement.

The tapered nut ljon the' threaded end I6 ofshaf-t 2 is recessed at its forwardv end' which overhangs'the splinedl section 8v ofthe shaft to enclose the spring I1 disposed'on'shaft 2. The washer' I8w is splined to fit splines 8V and closes the forward end of nut `I 5. The tabs I9 of washer I81are adapted to be bent rearwardly into corresponding sletsfZ` in the outeredge' of nut I5 to lockor prevent` loosening ott-he same on shaft 2.

` Thesplinedldisc 2I secured on 'sectiontoi' shaft 2 forwardly ofwasherr ISandthe friction di `sc22 between face II of hub 4 and vdisc 2| engaging splines I2o-f hub 4 provideabearing surface .supporting springv I1, as' will be described.

Nut. I5V isadjustedon the threaded end I6 of shaftl so thatspring I1 vexerts 'adenitelydetermined force againstwasher .I 8 forwardly on shaft Land-.againstdiscs 2I.and 122 and'face `I'I of hub 4. The biasingof hub, 4., forwardly ,on 'shaf-t clutch engagement for initial operation, as described above, obtains throughout the operation of the unit and so that the capacity of the clutch will not fall below the power output of the motor. The spring l1 thus provides a marginal capacity at all times which precludes the possibility of R. P. M., the propeller which is pressed forwardly by the thrust of the blades must move rearwardly on shaft 2 instantly thereafter to release immediately clutch unit 6 if damage to the propeller is to be avoided. Also, by disposing the discs forwardly of fthe solid section S of the propeller hub, as shown, an excessively long release stroke `is avoided while the required Thus, when a propeller blade 5 strikes Y through the rear bore, a nut turned and secured on the threaded end of said shaft, and a spring minimum capacity of clutch unit B is ensured by spring I1 which, is in operation at all times to effecta minimum clutch engagement of discs v I3 and I4l and which at all times throughout the range of operation of the propeller supplements the propeller thrust so that slippage of the propeller under excessive loads, asV under acceleration, is precluded.

Variousr embodiments of the invention may be employed within the'scope of the accompanying claims.

I- claim:

l. In an outboard motor and the like, apropeller having a series ofstepped bores extending centrally therethrough, said bores including Y an internally splined bore intermediate a larger bore opening forwardly of the hub and a smaller bore opening rearwardly of the hub with rei spect to the direction of normal propeller thrust, the section of said hub defining the rear bore providing an annular shoulder immediately to the rear of theintermediate bore and providing foppositely thereof thefrear face of the hub, the :forward section of the hub forming the forward .bore of a diameter at least equal that of the .maximum diameter of said intermediate splined bore, a propeller shaft having a shoulder facing Arearwardly and a rear threaded end, splines :formed in said shaft intermediate the shoulder and threaded end thereof, a thrust plate mounted on said splines'and against the shoulder of'said shaft, a seriesgof friction discs mountedon said shaft rearwardly of said thrust plate, alternate discs of` said seriesl being splined at the' inner circumference thereof and interlocked Vwith the splines ofsaid shaft and the other discsof Asaid series'being splined at ,the outer circumference thereof and interloclredwith the splined intermediate bore of said hub;said hub being rotatably mounted on/'said shaft Aand supported for limited axial movement in' the forwardi'bore on and with respect to said thrust platev and directly on and with respect to saidshaft passing disposed on said shaft intermediate said nut l and the rear face of said hub urging the latter forwardly on said thrust plate and shaft in the direction of propeller thrust, said discs being disposed between said thrust plate and said first named shoulder and urged in frictional inter-engagement to maintain a minimum rotativer driving connection between said shaft and said propeller subject to increase by the thrust of the propeller and subject to slippage upon overloading.

2. In an outboard motor and the like, a propeller having a series of stepped bores extending centrally therethrough, said bores including an internally splined bore intermediate a larger bore opening forwardly of the hub and a smaller bore opening rearwardly of the hub with respect to the direction of normal propeller thrust, the section of said hub defining the rear bore pro- Viding an annular shoulder immediately tothe rear of the intermediate bore and providing oppositely thereofthe rear face of the hub,A the forward section of the hub forming the forward bore of a diameter at least equal that of the maximum diameter of saidintermediate splined bore, a-propeller shaft having a shoulder facingv rearwardly and a rear threaded end, splines formed in said shafty intermediate the shoulder and threaded end thereof, a thrust plate mounted on said splines and against the shoulder of sai'dshaft, a series of friction discs mounted on said'shaft rearwardly of'said thrust plate, alternate'discs of said series being splined at the inner circumference thereof and interlocked with the splines of said shaft and the other Vdiscs of said series being splined at theV outer circumference thereof and interlocked with the splined intermediate Ibore of said hub, said hub being rotatably mounted on said shaft and supported for limited axial movement in the forward bore on and with respect to said thrust plate and diL rectly on and with respect to said shaft` passing through the Arear bore, and means includingra nut secured on the threaded end of said lshaft and securing the hub forwardly on said `thrust plate 'and shaft in -the direction of propeller thrust, said discs being disposed between said thrust` plate 'and said first named shoulder and secured in fr ictional inter-engagement to effect arotative drivingconnection between saidshaft and' said propeller subject to increase bythe thrust of the propeller and subject to 'slippage upon overloading of the propeller. f ELMER CsKIVEKHAEFER.

l REFERENCES CITEDl Y The following references are of record inthe file of 'this patent:

UNITED STATES PATENTS Number 'Y Dgg. Y

Name Y VV1,472,077 Lockwood 'Oct.`30, 1923 2,402,197- l' Kincannon J une 118,5, 1946 

